Icom IC-701 User Manual

3-9 EXTERNAL SPEAKER
The IC-701 contains an internal speaker, and is also
designed so that it can drive an external speaker from the
external (EXT) speaker jack on the rear panel. Be sure the
impedance of the external speaker is 8 ohms, and remember
that with the external speaker connected, the internal
speaker is disabled.
3-10 HEADPHONES
Any good headphone set, including stereo type, that have
4-16 ohms impedance can be used. With the plug inserted
halfway into the PHONES jack, both the headphone and
speaker will operate. This is convenient when others wish
to listen in on the station, or you wish to record contacts
using a tape recorder connected to the headphone jack.
With a stereo headphone set inserted this way, however,
the headphone will lose the sound on one side. With the
plug inserted completely, only the headphone works.
3-11 POWER SUPPLY
It is highly recommended that you use the [C-701PS power
supply for base operation. If you wish to use another
power source, make sure that it meets the voltage, current,
and regulation requirements. Pay particular attention to
the overvoltage protection as a runaway regulator can
destroy the IC-701. Make certain that more than 18 Volts
does not get applied to the unit. When the power switch
is in the ON position, do not connect the power cord,
antenna, external speaker, Accessory plug, or the mi-
crophone to avoid possible trouble. Be sure not to transmit
with the antenna disconnected. If the fuse blows, replace
it with a new 20 Amp fuse after fixing the cause. Avoid
turning
the
power
switch
ON
and
OFF
repeatedly
over
a
short time. Frequent repetitions may cause the frequency
indicator to display the wrong frequencies. If such a
malfunction should occur, turn OFF the switch and a few
seconds later turn it ON again.
3-12 CAUTIONS
As the unit has already been closely adjusted with highly
sophisticated measuring instruments, never tamper with
the turnable resistors, coils, trimmers, etc.
IN THE PLL UNIT, THE HEART OF THE TRAN-
SCEIVER, A C-MOS LSI IS INCORPORATED. IF THE
SEAL IS BROKEN WHEN A FAILURE OCCURS WITHIN
THE TERMS OF THE GUARANTEE, THE REPAIR
MAY BE AT THE USERS EXPENSE, SO DO NOT
ATTEMPT TO OPEN THE PLL CASE!
C-MOS is also used in the digital driver unit as well as the
PLL. C-MOS ICs are very susceptible to excessive static
charges and over current and care must be used when
handling them. Therefore, avoid touching the driver
unit and the nearby circuitry unless absolutely necessary.
When it is necessary to check the circuitry, observe the
following points.
Ground all measuring instruments, the soldering iron, and
other tools. Do not connect or disconnect the C-MOS IC
from its socket, or solder it when the power is ON. Do
not apply voltage of less than —0.5 or more than +5 Volts
to the input terminals of the IC. DO NOT MEASURE
WITH AN OHMMETER.
3-13 COOLING FAN
The rear of the PA unit is designed to achieve effective
natural cooling. But with 200 Watts input, the final stage
circuit produces quite a bit of heat and its temperature may
rise during a very long, continuous transmission. If the
temperature becomes high enough, the built-in cooling fan
will start to spin. The fan is connected to the temperature
monitoring circuit which detects the temperature of the
final stage transistors. The operation of this fan is as
follows:
1. The fan does not work during all reception.
2. During transmission, it does not work if the detected
temperature is below a certain level.
3. When the temperature exceeds that level during a
transmission, the fan will start to move air across the
heatsink to cool it.
4. If the temperature of the final stage transistors rises to
the danger point, the fan will turn at a much higher
speed and frequency display will start to flash.
THIS MEANS STOP TRANSMITTING!
1, 2 and 3 are normal conditions. 4 is abnormal. If the
meter and display start to flash, stop transmitting and
check for the cause of the excess heat. This could be
antenna mismatch, environmental problems, etc., but be
sure to rectify the problem before beginning to operate
again.
—5—
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Icom IC-701 Specifications

General

Brand	Icom
Model	IC-701
Category	Transceiver
Language	English